This mod replaces the stock seat bungs and replaces them with valves cut out of a cheap syphon pump. They are installed from the bottom side and pushed into position or tapped with a rubber mallet, then sealed with silicone.
Once they are installed the valves act like a venturi system, sucking out any water in the seat well. When you stop the valves float and seal themselves so you dont get any water coming back in.
You need 2 cheap syphon pumps as per the pic. These are readily available in Australia.
Cut out the exit valve (the top one) and the surrounding plastic. The surrounding plastic is inserted into the bung hole and provides a frame for the valve. It's a tight fit but goes in with a little tap. The below image is what you should be left with once cut out.
Insert into the bung hole and seal with silicone.
The valve flap must be facing backwards.
Smooth the silicone out and there you go. Simple and effective.
Thats it and one of the best mods I have done. The system has been in place for 4 months now without any issues at all. When your sailing you can hear them sucking the water out and when your parked nothing can get back in.